| dc.description.abstract | The anisotropic bubble collapse under the symmetry-breaking process was well studied in the past few decades, such as cavitation erosion, underwater explosion and acoustic wave-bubble interaction. Recently, the developed bio-technology of cell lysis and the micro-surgery in the laser-microscope system are associated with the laser induced cavitation bubbles and shock wave. Nevertheless, the mutual bubble interaction between the micro-bubbles with the cavitation induced shock wave and flow field are not studied. Moreover there is no clear physical picture of the detailed bubble fragmentation evolution associated with the complicated hydrodynamic interaction.
We experimentally investigate the pulsed laser induced two dimensional bubble interaction using high speed micro-photography. We address a new issue of the fragmentation dynamics about a strongly perturbed bubble with good reproducibility in a micro-gap. The topological patterns of the stationary bubble (B1) impacted by the nearby laser induced cavitation bubble (B2) are presented. Typical bubble (B1) deformations such as jetting, butterfly-shape pattern in fragmentation under various experimental conditions of geometry and laser power are studied. Due to the unstable liquid-gas interface of vapor bubble and the thermal effect of compressible bubble, the interaction process of B1 undergoes three stages, compression, re-expansion and collapse against the expanding and then collapsing B2. The forward liquid jet on B1 surface due to surface instability in the stage of compression protrudes the opposite bubble surface. The jet protrusion entrains vapor forward and leads to butterfly-like bubbles. In the stage of anisotropic re-expansion, the inward transverse jetting at the bubble neck fragments B1. Hence, the topology of bubble fragmentation is determined and then stabilized in the final stage of collapse. Furthermore, at short inter-bubble distance, the strong backward interactions for B2 are found, such as backward jetting and bubble mixing associated with the interplay between the collapsing B2 and the re-expanding B1. By the volumetric analysis, we explain the energy transfer between the two bubbles and the role played by B1 in the anisotropic liquid background compared with the free expansion of single bubble. In this thesis, the simplified 2D bubble interaction in the system without buoyancy force is studied first time, and the details are discussed. | en_US |